Alloys



L58 CONTRACTION- MlLS/IN. I. U7 L Q l Nov. 15, 1960 H. c. SMITH, JR2,960,402

ALLOYS Original Filed Jan. 21. 1958 TEMPERATURE OF RIGID BOND AxMIsMATcH5| eq- ALSIMAGGI (ATYPICAL HIGH ALUM.CERAMIC) -RODAR(ALLOY LEAD FORGLASS ELECTRONIC wees 5154- TEMPERATURE c ALLOYS Harry Clark Smith, Jr.,Upper 'Montclair, N.J., assignor to Wilbur B. Driver Company, Newark,N.J., a corporation of New Jersey Continuation of application Ser. No.710,264, Jan. 21, 1958. This application Oct. '6, 1959, Ser. No. 844,681

6 Claims. (Cl. 75-170) This invention relates to alloys consistingessentially of iron, nickel, and cobalt.

As is known, glass is normally used as a container, or envelope, forelectrical discharge devices. For ordinary leaded, or soft glass, nosubstantial problems have been experienced in providing leads for theelectrical discharge elements which have appropriate expansivity andcontraction characteristics to form and retain hermetic seals with theglass when the glass is heated to annealing temperatures and thereafterpermitted to cool to room temperature before being used. For instance,ordinary nickel-steel alloys jacketed with copper have provensatisfactory. For certain types of high melting hard glass, such asboro-silicate glass, some difiiculty has been experienced in findingleads which have characteristics suitable for forming and retaininghermetic seals with this type of glass. Yet this type of glass is, attimes, needed in modern electronic equipment. Special iron-nickel-cobaltalloys have been developed and proven most economical and satisfactoryfor the purpose of forming vacuum-tight seals with such glass envelopes.Yet all types of glass begin to lose their dielectric properties whenelectrical discharge devices are operated at high frequencies and atelevated temperatures.

On the other hand, high alumina ceramics are known to retain theirdielectric properties at high frequencies and are known to have goodstrengths at elevated temperatures. Thus, electronic manufacturers havebeen interested for some time in the substitution of high aluminaceramics as a vacuum tube envelope for electrical discharge devices. Yetthe special alloy leads heretofore developed for use with glassenvelopes have not proven satisfactory as leads for such ceramicenvelopes, since they are not well adapted for forming and retaininghermetic seals with high alumina ceramics. As a re sult, high aluminaceramics have not heretofore been successfully used for vacuum tubes orthe like. For the same reasons, it has been very diflicult to formsatisfactory hermetic seals with high alumina ceramics used for otherpurposes such as for bushings used in small transformers developed foraircraft use.

It is a principal object of this invention to provide alloys havingexpansion and contraction properties sufficiently close to those of highalumina ceramics to permit forming and retaining hermetic seals betweenthe alloy and high alumina ceramics.

It is a special object of the invention to provide alloys adapted foruse as a lead which will form a vacuum-tight seal through a high aluminaceramic envelope for a vacuum tube containing an electric dischargedevice.

nited States Patent 2,960,402 Patented Nov. 15, 1960 It is an importantobject of the invention to provide an alloy which will have a maximumcontraction mismatch between hermetic sealing temperatures with a highalumina ceramic and room temperature which does not substantially exceedthe mismatch at room temperatures.

Other objects of the invention will be apparent from the description ofthe invention which follows.

It has been discovered that the foregoing and other objects of theinvention can be achieved by providing a basically ternary alloyconsisting essentially of 24- 29% cobalt, and the remaindersubstantially only nickel and iron in a ratio of about 56-571100.Customarily, such an alloy may contain about 1%, or less, of manganeseand other impurities. Very satisfactory alloys have been prepared havingfrom 24-25% cobalt, say about 24.5 cobalt, and the remaindersubstantially only nickel and iron in the stated ratio. 'For instance,such an alloy could consist essentially of about 26.7% nickel, 24.5%cobalt and the remainder substantially iron. More particularly, analloy, designated herein as alloy 5164, containing about 26.80% nickel,about 24.44% cobalt, about 47.31% iron and about .49% manganese hasproved well adapted for use as a lead for a high frequency electricaldischarge device and yet will form a vacuum-tight seal with a highalumina ceramic, preferably containing 90-95% alumina, serving as avacuum envelope for the discharge device. Vacuum tubes provided withsuch leads retain the originally established vacuum-tight seal and havethe advantage of retaining their dielectric properties after extendeduse at high frequencies, and where necessary, at elevated temperatures.

Another, but slightly less-advantageous, alloy designated herein asalloy 5303 has been prepared contain ing about 25.5% nickel, 28.5%cobalt, and about 46.3% non.

Such alloys may be hermetically sealed to such high alumina ceramics foruse in other devices such as the transformer bushings previouslymentioned.

It will be understood that a high alumina ceramic, as used herein,relates to a ceramic containing -95% alumina, preferably -95% alumina,and the remainder principally silica. It may also include some complexsilicates as impurities.

The advantages of this invention will become apparent from a comparisonof the contraction characteristics of a high alumina ceramic containing90-95% alumina with (a) a typical iron-nickel-cob-alt alloy, Widely usedas a lead for vacuum tubes made of glass and (b) the above mentionedalloys 5164 and 5303. Sui able high alumina ceramics containing 90-95%alumina are available from various sourcm, but such a ceramic obtainablefrom the American Lava Corporation, Chattanooga 5, Tennessee, under thedesignation of Alsimag 614, has been used for purposes of comparison.Iron-nickelcobalt alloy leads for glass vacuum tubes are available fromvarious sources. An alloy containing about 29.0% nickel, 17.5% cobalt,53.2% iron, and 0.3 manganese, "obtainable from Wilbur B Driver Company,Newark, N.J., under the designation of Rodar is consideredrepresentative and has been used for purposes of comparison.

The comparisons are shown in the table below. In the table, thecontraction mismatch is expressed in mils/inch and is determined byassuming the ceramic and the alloy have the same dimensions at 750 C.,

which is the melting point of a typical silver solder used for brazingthe ceramic and the metal together. The inflection temperature is thetemperature at which the rates of contraction or expansion of therespective alloys increase.

Max. Temper- Infleo Misature tion match Max Alloy Ni Fe Co ,Mn Temp.from Mis- I O. Alsimag match 614 I C Mils/lnch Rodar 29. 0 53. 2 17. 530 437 2. 2 410 5164..- 26.80 47.31 24.44 49 542 1.45 500 5303"" 25.246.3 28.5 570 1.55 25 5303 has its greatest mismatch at 25 C., namely1.55,

and the greatest mismatch between room temperature 750 C. at 550 C.namely, 1.46 mils/inch. These two values likewise are very close. Itwill be observed that the maximum mismatch of the Rodar standard in eachinstance is almost 50% more than that of alloy 5164 and alloy 5303.

This application is a continuation of the application 4 of Harry ClarkSmith, In, Serial No. 710,264, filed January 21, 1958, now abandoned.

It will be understood that the foregoing description of particularembodiments of the invention are for illustrative purposes and thatmodifications in details may be made by those skilled in the art withoutdeparting from the scope or spirit of the invention as defined in theappended claims.

I claim:

1. An alloy consisting essentially of about 24-29% cobalt and theremainder nickel and iron in a ratio of about 5657:100.

2. An alloy consisting essentially of about 26.7% nickel, about 24.5%cobalt and the remainder substantially iron.

3. An alloy consisting essentially of about 26.80% of nickel, about24.44% of cobalt and about 47.31% iron.

4. An alloy consisting essentially of 24-25% cobalt, and the remaindersubstantially nickel and iron in a ratio of about 56-57 :100.

5. An alloy consisting essentially of about 25.2% nickel, 28.5% cobalt,and about 46.3% iron.

6. As an article of manufacture, a composite structure comprising a highalumina ceramic bonded to an alloy consisting essentially of 24-29%cobalt and the remainder substantially nickel and iron in the ratio ofabout 56-57zl00, said structure providing a vacuumtight seal at thebondbetween the ceramic and the alloy.

References Cited in the file of this patent Scott: Transactions of theA.I.M.E (Institute of Metals Division), 1930, pages 506-537.

Metals Handbook, 1948 ed., page 173.

1. AN ALLOY CONSISTING ESSENTIALLY OF ABOUT 24-29% COBALT AND THEREMAINDER NICKEL AND IRON IN A RATIO OF ABOUT 56-57:100.
 6. AS ANARTICLE OF MANUFACTURE, A COMPOSITE STRUCTURE COMPRISING A HIGH ALUMINACERAMIC BONDED TO AN ALLOY CONSISTING ESSENTIALLY OF 24-29% COBALT ANDTHE REMAINDER SUBSTANTIALLY NICKEL AND IRON IN THE RATIO OF ABOUT56-57:100, SAID STRUCTURE PROVIDING A VACUUMTIGHT SEAL AT THE BONDBETWEEN THE CERAMIC AND THE ALLOY.